There are a lot of subtleties. Ring species are a particularly fun one: you can have a population that live around some natural obstacle (like a large body of w

There are a lot of subtleties. Ring species are a particularly fun one: you can have a population that live around some natural obstacle (like a large body of water) where individuals can breed successfully with individuals near to them but not with ones further way (like directly across the barrier), in a continuum of variation.